Chickenpox is caused by the highly contagious varicella zoster virus. It is spread by coughing and sneezing, and by direct contact with skin lesions. Chickenpox can lead to severe complications, including bacterial infection of the skin from the lesions, swelling of the brain, and pneumonia. Adults are at greater risk for severe complications from chickenpox than children.
Once a person has had chickenpox, the virus can reactivate later in life to cause a painful condition called shingles, marked by a blistering rash.
Learn more about chickenpox and the vaccine to prevent it.